[mythtv-users] Banding, noise and other gremlins

[Anil Gupte]

Here is what I found.  We used a different power supply and the banding/snow 
went away.  I am still trying to figure out if the power supply was better or 
whether it has more juice.  In theory the power supply causing the problems is 
better because it is rated at 400w and the one that fixed the problem was 285 
watts, but who knows what the truth is.  Also, after the fact I remember that we 
never actually put the other power supply into the case, so just being far away 
from the PVR-350 may have the difference.

Any thoughts will be welcome and I will keep you informed.

Thanx,
Anil Gupte
www.keeninc.net
www.icinema.com

----- Original Message ----- 
From: "Anil Gupte" <anil-list at icinema.com>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Saturday, April 29, 2006 1:37 PM
Subject: Re: [mythtv-users] Banding, noise and other gremlins


Thanx for the advice, Steven and William.  I am going to try those things.
Unfortunately, it is hard to get filtered power strips here (believe it or not)!
I am trying to get an electrician in there to check the circutis and also call
the Cable TV guy to check his grounding.  I will report back on what I find.

Anil Gupte
www.keeninc.net
www.icinema.com

----- Original Message ----- 
From: "Steven Adeff" <adeffs.mythtv at gmail.com>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Wednesday, April 26, 2006 7:09 PM
Subject: Re: [mythtv-users] Banding, noise and other gremlins


> ----- Original Message -----
> From: "Steven Adeff" <adeffs.mythtv at gmail.com>
> To: "Discussion about mythtv" <mythtv-users at mythtv.org>
> Sent: Tuesday, April 25, 2006 8:14 PM
> Subject: Re: [mythtv-users] Banding, noise and other gremlins
>
>
> On 4/25/06, Anil Gupte <anil-list at icinema.com> wrote:
> > I installed a box (running mythtv 0.18 with PAL PVR 350) in a friends house
> > and he is having problems with banding (dark and light) as well as bands of
> > "noise" (like snow) on the screen.  I used it at my friend's house on a
> > different TV and the problem was minimal but still there.  I used the same
> > box at my home and had no problem.  Someone I showed it to says it is caused
> > by Electromagnetic Interference (EMI).  Is that a good explanation?
> >
> > Is there any other explanation?  What fixes should I try?  Can this be
> > caused by grounding problems in the electrical circuit or improper grounding
> > in the cable TV (they have multiple connections in the house)?  The same guy
> > who diagnosed EMI suggested I try a power strip with RF filtering.  Where
> > can I find such a beast?
> >
> > Thanx in advance for any and all advice.
> > Anil Gupte
>
> do you see these effects when not connected through Myth?
On 4/26/06, Anil Gupte <anil-list at icinema.com> wrote:
> No.  Only when Myth was connected.  Direct from Cable TV to the TV there is no
> problem.  Now that I think about it I think it is an electrical problem
> because
> I could see this even when the Cable TV cable was not connected to the Myth
> box.

Try disconnecting the cable TV cable and playing back a DVD through
Myth to the TV. If you see the issue then you can rule out the cable
line as being the problem. If you don't, then connect the cable line
and again play a DVD, if you see the problem then you most likely have
a ground voltage difference between the cable line and your outlet's
ground. One way to solve this is to ground the cable line using a home
theatre power strip that does cable filtering/ground. The other is to
get a ground block from a home hardware or home electronics store.
This will mount to a wall and has a screw to run a wire to an outlet's
ground (in the US its the center screw that the wall plate is held in
with).

I'd suggest going with a home theatre power strip that does filtering
if you don't have one already. Panamax is my prefered brand and for
about $30 you can get a power strip that will have cable filtering.
You can plug your computer and your TV, etc into it as well. This will
protect your equipment from power spikes and filter out any line noise
if you have any on the circuit.

--
Steve
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